The term "III-V semiconductors" is used to describe crystalline materials or solid solutions formed from substantially equimolar amounts of at least one element from group IIIb of the Periodic Table of the Elements (B, Al, Ga, In, and Tl) and at least one element from group Vb ,of the Periodic Table of the Elements (N, P, As, Sb, and Bi).
Several III-V semiconductors exhibit feature which make them attractive for use in solid state electronic devices (e.g., high thermal stability, high electron mobility, and low band gap). However, the III-V semiconductors are more difficult to synthesize than the widely used group IV semiconductors, and the lack of suitable routes to the III-V compounds has hindered their acceptance as alternates to the group IV compounds.
C. Hilsum et al., "Semiconducting III-V Compounds", Pergamon Press, New York, 1961, review the preparation of many III-V semiconductors by direct combination of the elements. Although this method is applicable to the synthesis of several III-V compounds, special equipment and techniques are required to safely handle the high temperatures and/or high pressures encountered in synthesis. A. H. Cowley et al., Angew. Chem. Int. Ed. Engl., 28, 1208 (1989). U.S. Pat. No. 3,309,176 discloses a route to III-V compounds comprising heating an intimate mixture of the elements with a small amount of halogen gas in a closed and (partially) evacuated vessel. Preferably, the temperature of the reaction zone is between 550.degree. C. and
U.S. Pat. No. 3,947,549 disclose the preparation of III-V materials (AlN, InN, InP, and GaN) by reacting a hydride of nitrogen or phosphorus with a halide of Al, In, or Ga in the gas phase at a temperature below the decomposition temperature of the III-V material. The temperature of the reaction is at least 400.degree. C.
British Pat. No. 1,180,314 discloses a process for the production of GaAs, which comprises contacting a pulverous gallium alkoxy halide with arsine at a temperature in the range of from 300 to 800.degree. C.
Recently, metal-organic chemical vapor deposition (MOCVD) routes to III-V semiconductor thin films have become increasingly attractive, due largely to the high growth rates, high purity, high crystal quality, and ease of process control. MOCVD involves impinging a stream of cool gaseous reactants (e.g., trimethyl gallium and arsine), usually in admixture with a carrier gas (e.g., hydrogen), onto a hot substrate to form the III-V semiconductor. (See, for example, Manasevit, Appl. Phys. Lett., Vol. 12, p 156, 1968.)
U.S. Pat. No. 4,436,769 disclose a method of depositing a group III element-group V element compound or alloy on a hot substrate using a MOCVD procedure. This procedure uses a modified alkyl derivative of the group III element, wherein either an electron donating group is substituted for one of the alkyl groups of the group III compound or the group III element alkyl derivative is combined with an alkyl derivative of a group V element to form a volatile compound. The temperature of the substrate is typically between 600.degree. C. and 700.degree. C.
U.S. Pat. No. 4,716,130 discloses an MOCVD process which uses ferrocene or iron pentacarbonyl based compounds in the preparation of semi-insulating epitaxial layers of InP-based compounds. The substrate was heated to 650.degree. C. to 700.degree. C.
Cowley et al., J. Amer. Chem. Soc., Vol. 110, pp 6248-6249, 1988, disclose organometallic chemical vapor deposition of III/V compound semiconductors. For example, [Me.sub.2 Ga(.mu.-t-Bu.sub.2 As)].sub.2 is used as the single source for the production of GaAs films. Film growth conditions involve the use of a cold-wall reactor, H.sub.2 or He as the carrier gas, maintenance of the saturator containing the organometallic source at 130.degree. C. substrate temperatures of 450 to 700.degree. C., and a total system pressure of 1.times.10.sup.-4 to 10 torr.
These methods for preparing III-V semiconductors reviewed herein either require high temperatures in the gaseous reaction zone or of the substrate, or are specific to only one species of III-V compound.
It is an object of the present invention to provide a low temperature synthesis of semiconducting group III-group V material. It is a further object of the present invention to provide a semiconducting group III-group V material useful to form semiconductors having utility in solid state electronics and other fibers. A feature of the present invention is its applicability to group III-group V semiconductors including one or more elements selected from each group. An advantage of the present invention is the ability to form semiconductors without employing high temperatures to the reactants or to a substrate. These and other objects, features, and advantages of the present invention will become more readily understood and appreciated upon having reference to the following description of the invention.